Fig.42.12 ]).Affectedindividualshavesevereintellectualdisability,shortstaturewithincompleteskeletaldevelopment,coarsefacialfeatures,andaprotrudingtongue.Themostcommoncauseofhypothyroidisminchildrenworldwideisiodidedeficiency.Historically,iodidedeficiencywasviewedasamajorcauseofhypothyroidismincertainmountainousregionsofSouthAmerica,Africa,andAsia,butrecentevidencesuggeststhattheproblemisevenmorewidespread.Thistragicformofendemic hypothyroidism canbepreventedbypublichealthprogramsthataddiodidetotablesaltorprovideyearlyinjectionsofaslowlyabsorbediodidepreparation.Congenital defects arealesscommoncauseofneonatal/childhypothyroidism.Inmostcasesthethyroidglandsimplydoesnotdevelop(thyroid gland dysgenesis). Lessfrequentcausesofchildhood •Fig. 42.12 A,Normal6-year-oldchild(left) andacongenitallyhypothyroid17-year-old(right) fromthesamevillageinanareaofendemichypothyroidism.Notetheshortstature,obesity,malformedlegs,anddullexpressionoftheintellectuallydisabledhypothyroidchild.Otherfeaturesareaprominentabdomen,aflatbroadnose,ahypoplasticmandible,dryscalyskin,delayedpuberty,andmuscleweakness.Radiographsofthehandcomparinganormal13-year-old(B)tothatofa13-year-oldsufferingfromhypothyroidism(C).Notethatthepatientwithhypothyroidismhasamarkeddelayindevelopmentofthesmallbonesofthehands,ingrowthplatesateitherendofthefingers,andinthegrowthplateofthedistalradius.(A,FromDelangeFM.In:BravermanLE,UtigerRD[eds].Werner and Ingbar’s The Thyroid. 7thed.Philadelphia:Lippincott-Raven;1996.B,FromTannerJMetal.
Assessment of Skeletal Maturity and Prediction of Adult Height (TW2 Method). NewYork:AcademicPress;1975.C,FromAndersenHJ.In:GardnerLI[ed].Endocrine and Genetic Diseases of Childhood and Adolescence. Philadelphia:Saunders;1975.) hypothyroidismaremutationsingenesinvolvedinthyroidhormoneproduction(e.g.NIS,TPO,thyroglobulin,pendrin)orblockingantibodiestotheTSHreceptor.Theseverityoftheneurologicalandskeletaldefectsiscloselylinkedtothetimingofdiagnosisandthyroidhormone(T4)replacement,withearlytreatmentresultinginanormalcognitiveabilityandsubtleneurologicaldeficits.Ontheotherhand,ifhypothyroidismatbirthremainsuntreatedforonly2to4weeks,theCNSwillnotmaturenormallyinthefirstyearoflife.Developmentalmilestonessuchassitting,standing,andwalkingwillbelate,andsevereirreversiblecognitivedeficitscanresult.Hypothyroidbabiesusuallyappearnormalatbirthbecauseofprotectionbymaternalthyroidhormones.Neonatal screening (T4andTSHlevels)hasthereforeplayedacriticalroleindiagnosisandpreventionofcongenitalhypothyroidism.